The focus of this research proposal is to design novel long-lasting antioxidants, termed self-cyclizing antioxidant reagents. This proposal is significant because the novel chemistry developed will result in a new sunscreen additive and oxidative damage reducer. Exposure to ultraviolet radiation has been linked to melanoma incidence with critical classes of individuals requiring more sunscreen protection. There is a strong technological driving force within this proposal since more sunscreen protection schemes against UV-induced damage are needed. Current sunscreens rely on two classic mechanisms with this proposal seeking to add a long lasting, catalytic, and safe antioxidant component. Neither of the classic mechanisms deals with the problem of ?dark damage? that is comprised of persistent radical formation for long periods of time after ultraviolet exposure. Development of self-cycling antioxidant reagents that address the above limitations, are selectively activated in cells with toxic reactive oxygen forms, and then liberate an inhibitor of the Nox1 haloenzyme for general ROS reduction are underway. The long-term goal is to show that ROS detoxification agents in sunscreens are advantageous. The premise is that the lack of effective antioxidants in sunscreen applications can be overcome by designing a catalytic ROS reducer that is only triggered by the most toxic ROS forms. The hypothesis is that self-cyclizing antioxidant reagents can prevent damage long after exposure to UVR by releasing an oxidase inhibitor. The Aims are: (1) Improving selectivity and inhibition of self-cyclizing antioxidants. Synthesis of reagents that have better oxidase inhibition and do not possess problematic phenols are planned. Targets were identified through docking studies that improved on the structure of apocynin. The most promising will be linked to self-cyclizing antioxidant reagents to impart selectivity. Students will synthesize ~15 molecules per year, examine binding, and quantify UV-induced viability rescue in primary skin cells. The next aim is (2) Reduced UV-damage and distribution in skin explants. Data shows a molecule that can limit UV-induced p53 expression and lower cyclobutane pyrimidine dimers in authentic human skin explants. Activity assays for DNA repair will be assessed to determine differential effects. Next, skin explant distribution and comparison with commonly used sunscreen antioxidant additives will be accomplished. The outcome of this research is to develop an additive that can safely and effectively reduce UV-induced dark damage as a final line of defense. Strong preliminary data supporting the hypothesis and a team, comprised of students, with chemical and skin biology experience can complete the Aims. This AREA proposal will give students valuable research experience in the life sciences and strengthen the research environment. With the successful completion of this study we will have a reagent that is ready for safety testing in the future. !